1. Field of the Invention
The invention relates to liquid crystal display (LCD) devices, and in particular to single layer color cholesteric liquid crystal display devices and fabrication methods thereof.
2. Description of the Related Art
Liquid crystal display (LCD) devices have many advantages such as a smaller size, lighter weight and lower power consumption, and are applicable in a variety of electronic and communication devices including notebook computers, personal digital assistants (PDA), mobile phones and the like due to its lighter weight, thinner profile, and portability. Conventional reflective memorable color liquid crystal display devices are widely applicable in electronic books, electronic papers, and the likes. The structures and fabrication methods of conventional cholesteric liquid crystal display devices use a tri-layered red (R), green (G), and blue (B) pixel stacked structure corresponding to various different driving methods. However, stacking tri-layered R, G, and B pixels may result in optical aberration and misalignment during fabrication. Moreover, the tri-layered R, G, and B liquid crystal layer stacked structure are so complicated that layout of electrodes is difficult to design and an LCD panel using the stacked structure has a rigid port, resulting in an intricate fabrication processes and high fabrication costs.
Accordingly, the use of single layer color cholesteric liquid crystal display devices and fabrication methods thereof can effectively ameliorate optical aberration, simplify the fabrication process, and reduce fabrication costs. Particularly, the device is applicable to the field of color flexible LCD devices. U.S. Pat. No. 5,825,451, the entirety of which is hereby incorporated by reference, discloses a single layer color cholesteric LCD device using a combination of light decomposable/polymerizable chiral agents and single layer cholesteric LC structure. The single layer color cholesteric LCD device is illuminated by a UV light disrupting or reducing contents of chiral agent at a single region to achieve colorizing of single layer cholesteric LCD device. However, the single layer color cholesteric LCD device is easily affected by ambient light deteriorating display stability thereof.
U.S. Pat. No. 6,741,321, the entirety of which is hereby incorporated by reference, discloses an LCD device using a single LC layer and a double substrate assembly process. Different color LC materials are respectively injected into LC channels during fabrication. However, the single layer LCD assembly is not sealed enough such that overflow occurs between adjacent LC channels resulting in color mixing and reduced color saturation.
FIG. 1A is a cross section of a conventional single layer color cholesteric LCD device. Referring to FIG. 1A, a conventional single layer color cholesteric LCD panel 2 includes a lower substrate 6 and an upper substrate 12 opposed to each other and with a gap therebetween. An enclosed structure 8 is interposed between the lower substrate 6 and the upper substrate 12, dividing a plurality of stripe color sub-pixel LC channels. A first electrode 4 and an alignment layer 14 are disposed on the lower substrate 6. A second electrode 10 and an alignment layer 14 are disposed on the upper substrate 6. The first electrode 4 and the second electrode 10 are substantially perpendicular to each other.
FIG. 1B is a schematic view of the lower substrate of the conventional single layer color cholesteric LCD device of FIG. 1A. In FIG. 1B, the enclosed structure 8 divides a plurality of (R, G, B) stripe color sub-pixel LC channels CR, CG, and CB. Perpendicularly crossed segments 16 and 18 are disposed on one end of the LC channels CG and CB to seal the LC channels. After the lower substrate 6 and upper substrate 12 are assembled, the second end L2 of the enclosed structure 8 are sealed by a sealant enclosing the LC channels CG and CB, while the first end L1 of the LC channels CR remains opened to serve as an LC injection opening. Each of the LC channels CR, CG, and CB is sequentially injected with respective color LC and sealed. Before filling each of the single layer color LC channels, however, conventional methods require sealing of the second end of the enclosed structure. Furthermore, when separately injection LC into the LC channels, different color LCs may overflow to adjacent LC channels and mix, thus resulting in color mixing and reduced color saturation.